Centrifugal pump or compressor



May 18, 1954 R. M. WATSON 5 CENTRIFUGAL PUMP 0R COMPRESSOR Filed March18, 1950 I 6 Sheets-Sheet 1 RALPH M. WATSON INVENTOR.

midi-1 May 18, 1954 R. M. WATSON CENTRIFUGAL PUMP OR COMPRESSOR 6Sheets-Sheet 2 Filed March 18, 1950 INVENTOR.

RALPH mwATsoN M ER May 8. 1954 R. M. WATSON 2,678,606

TS O'N VENTOR.

May 18, 1 954 R. M. WATSON 2,678,606

CENTRIFUGAL PUMP OR COMPRESSOR Filed March 18, 1950 r 6 Sheets-Sheet 4RALPH M.\/\/ATSON INVENTOR.

' May 18, 1954 R. M. WATSON CENTRIFUGAL PUMP 0R COMPRESSOR 6Sheets-Sheet 5 Filed March 18, 1950 May 18, 1954 R. M. WATSON 2,678,606

CENTRIFUGAL PUMP 0 COMPRESSOR Filed March 18, 1950' 6 Sheets-Sheet 6 INV EN TOR.

Patented May 18, 1954 UNITED STATES PATENT OFFICE WorthingtonCorporation,

Delaware a corporation of Application March 18, 1950, Serial No. 150,435

7 Claims.

This invention relates generally to multi-stage centrifugal pumps andcompressors for fluids of high or Varying temperature, and especiallyfor liquids of high delivery pressure, possibly in excess of a thousandpounds per square inch, and provides novel means for minimizinglongitudinal forces in the casing and its end closure joints, in spiteof differential thermal expansion of its members, and also forminimizing leakage at the shaft seals in each end of the casing, whileminimizing first cost and promoting easy inspection, repair andreplacement of parts.

While this invention will be described and shown in connection withpumps for high temperature liquid such as those for boiler feed in highefiiciency steam power plants, for petroleum products in oil refineriesand other liquids in chemical industries, it is not intended to so limitthis invention, which may be advantageously applied to multi-stagecompressors in which the pressure ratio results in a substantial rise intemperature of discharge gases or vapors during compression.

My invention is preferably applied to those high pressure multi-stagepumps that are of double casing construction, in which there is an outercasing of generally cylindrical form Without longitudinal jointssubjected to the delivery pressure of the fluid, and inside of it, aninner casing of horizontal split type enclosing all of the pumpimpellers, and fluid flow passages between the impellers. Such pumpsmust have at least one end of the outer casing open, with a boltedclosure member to permit insertion and removal of the inner casingassembly, and there must be a connection between these two members thatwill permit of independent longitudinal expansion and contraction due tochanges in the fluid temperature, to minimize longitudinal stresses inthe outer casing and limit the load on its end closure member and itsfastening, with prevention of leakage of fluid at the delivery pressure.It is recognized that an outer round casing without longitudinal joints,and an inner casing having a longitudinal joint, with the fluid deliverypressure between them, tending to burst the outer casing and to collapsethe inner casing, and to tighten its longitudinal joint, areadvantageous and in actual use.

However, this construction has developed two main problems. First, sincethe discharge pressure acts on the end closure of the outer casing,heavy flanges and bolts must be provided to prevent leakage as well asrupture. These heavy flanges and bolts increase the cost of manufactureand create an awkward and heavy structure to handle when repairs arenecessary. Second, the sealing structures between the shaft and theouter casing end closure member will be expensive or unsatisfactory ifsubjected to the delivery pressure that acts on the end closure member.

The present invention in a single embodiment contemplates a constructionwherein the delivery pressure, which acts between the inner and outercasing, does not act on an appreciable area of the end closure membersof the outer casing, and thereby does not load it, or longitudinallyload the outer casing, and at the same time prevents the deliverypressure from acting on the shaft seal in the end closure member, andpermits com plete freedom of thermal expansion of one casing relative tothe other.

Accordingly, it is an object of the present in vention to provide adouble case multi-stage centrifugal pump with the discharge pressureacting inside of the outer, and outside of the inner case, withoutproducing any opposing longitudinal forces in the outer casing, 0rsubstantially none, or loading its end closure members.

It is another object of the present invention to provide a novelconstruction of a double case multi-stage centrifugal high pressure pumpor compressor wherein the function of the outer casing will be simplythat of a cylindrical internal pressure resisting element carryingprimarily hoop stress instead of a combined hoop stress and axialstress.

It is another object of the present invention to provide a novelconstruction of a double case multi-stage high pressure pump with thedischarge pressure acting on the inside of the outer cylindrical case,but caused to act on a relatively small axially projected area of theend closure.

It is another object of the present invention to provide a novelconstruction of a double case multi-stage centrifugal pump with thedischarge pressure acting between the two cases, and the suctionpressure acting on both shaft stufiing boxes or seals.

It is another object of the present invention to provide a novelconstruction of a double case multi-stage high pressure pump Orcompressor wherein the whole sub-assembly, including impellers,connecting passages and inner casing can be assembled with its bearingsand checked for free rotation (before insertion into the outer casing orbarrel).

It is another object of the present invention to provide a novelconstruction of a double case multi-stage centrifugal pump with thedischarge pressure acting between the two cases for a longitudinaldistance limited to the space between two cylindrical piston lilzeextensions on the outside of the inner case contact with a boredinternal cylindrical surface on the inside of the outer case.

It is a further object of the present invention to provide at least oneor more slip joints between the contacting inner and outer cylindricalsurfaces of the inner and outer casings, which permits relative axialthermal expansion, under vari ations in temperatures, between the innerand outer casing also permits easy assembly and disassembly.

With these and other objects in view, as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing a centrifugal pumpor compressor of a preferred form embodying the invention, and thefeatures forming the invention will be specifically pointed out in theclaims.

In the drawings:

Figures 1A and 13 combined show a longitudinal section through amulti-stage centrifugal pump const noted in accordance with the presentinvention.

Figure 2 is a cross section through the pump casing taken on the line 22of Figure 1, looking the direction of the arrows.

igure 3 is a cross section through the pump casing taken on the line 3-3of Figure 1, looking inthe direction of the arrows.

Figure 4t is a cross section taken on the line 4-4 of Figure 1, lookingin the direction of the arrows.

Figure 5 is a longitudinal section through a slightly modified form ofthe invention.

Figure 6 is a fragmentary longitudinal section through a modified formof the pump embodying packing at the slip joint.

Figure '7 is a fragmentary longitudinal section through a modified formof the pump embodying rings at the slip joint or joints.

Figure 8 and Figure 13 combined show a longitudinal section through amodified form of the invention.

Referring more particularly to the drawings. Figures 1A 13 combined.show a preferred form of the improved multi-stage centrifugal pumpcomprising an outer casing l which is preferably of the barrel type,that it is a cylindrical casing open at one end to receive the innercasing 2 of the ump and being without any longitudinal joint. It beingunderstood that while this type of construction is called the preferredform, it is not intended to so limit the invention as the outer casingmay be constructed with both ends open as is shown in the modified formof Figures 8 and 13 combined.

Thus. in the preferred form, outer casing is open at the discharge endof the pump so that the inner casin 2 carrying the various impellers 3,and i l and having various flow passages t formed therein may beinserted longitudinally into the outer casing l with the suction eye 5of the first stage impeller 5 opening into the suction passage 1 formedin the end of the outer casing. A suitable sealing structure 8 for theimpeller shaft 9 is carried by the outer casing l at the inlet end ofthe pump and a corresponding sealing structure I!) is detachably carriedby the inner casing 2 at the discharge end of the pump. It is to beunderstood, of course, that bearings for the shaft 9 are provided beyondthe sealings 8 and ill, but such bearings may be of any approvedconstruction and are not shown in the present drawings.

The inner casing 2 is split longitudinally as is clearly shown inFigures 2, 3 and 4 of the drawings and its two sections H and i2 areconnected final stage impeller It di charges through the dischargeoutlet of the inner casing 2 into and through the outlet [5' of theouter casing i, across a gap or open space H, in communication with theannular space is between the inner and outer casings. V

In the preferred form of the invention the inner casing 2 has one ormore diametral enlargements l9 and 23 substantially piston-like inconstruction and disposed, so that there will be at least one of saidpistondike members at each end of the inner casing 2. Thus the dischargeoutlets 15, and iii and the space or gap ll will be dis.- posed betweenthe. piston-like enlargements l9 and 2G and the suction inlet 3' will bedisposed outwardly thereof. so that the suction inlet 1 and thedischarge outlets i5 and it will bev separated by at least one of saidpiston-like members, all of which is clearly shown in Figures 1A and 1Bof the drawings.

The piston-like. enlargements l5 and 2B are machined to make a slidingfit with corresponding inner circumferential bores 2i and 22, formed inthe bored interior'of the outer casing l. The bores 25: and 22 may be ofequal diameters with respect to each other but of lesser diameter thanthe inner circumference of the outer casing I. However, in the preferredform, bore 22 at the open end of the outer casing will have a littlelarger diameter than bore 2 l to facilitate the insertion and removal ofthe inner casing as. a single self contained unit.

In addition, if the bores 22! and 22 are of equal diameters the deliveryfluid acting between the piston members :9 and 2!! by reason of the gapi! cannot produce a longitudinal thrust in either direction. However,where the diameter of the bore 22 and correspondingly the piston 26 areof slightly larger diameter, there is a thrust force toward the open endof the outer casing as small as may be desired.

This unbalanced longitudinal end thrust may accordingly be adjusted to apredetermined limited magnitude whereby it will require only arelatively light flange and stud bolt to resist it. Figure 1B shows arelatively light flange 23 formed on the piston 29 which issubstantially annular in shape and is adapted to engage studs 2 on theopen end of the outer casing and to be held thereto by means of nuts 25,thus closing the outer casing both axially and longitudinally andproviding means for fixing the inner casing and its sub-assembly partsat only one end. This allows the inner casing and its subassembly to befree to expand and contract longitudinally within the outer casing bythe sliding of the piston l9 in the bore 2! formed in the outer casingbetween the suction inlet l and the discharge outlets I5 and I6 thereof,thus forming a relatively simple slip joint, all of which is clearlyshown in Figures 1A and 1B of the drawings.

The finished outer surface of the piston l9 may be provided withpressure reducing grooves ,26 to reduce the fluid leakage from theannular s'pace'lB between the inner and outer casings which receivesdischarge fluid pressure therein by reason of gap H, to the suction I,it being understood that other suitable means may be utilized such aspacking rings, rings or soft packing as is shown at 26a in Figure 6 and26b in Figure 7 of the drawings.

This slip joint between the inner and outer casings is made possible,practical, and commercially acceptable, due to the recognition by thepower and process industries that stainless steels around the waterwaysor liquid passages are preferable with present day boiler feedwaters andprocess industry liquids. Such stainless steels or materials areexceedingly resistant to corrosion and. erosion, and as the inner casingis made of stainless material, any slight leakage developing at the slipjoint between the high pressure and low pressure side would have a verylow rate of erosion and the life of the pump will accordingly beacceptable, and accumulation of corrosion products that might resistsliding is unlikely.

To prevent action of the discharge pressure on it, and to alternativelysubject the packing structure iii to the lowest unit pressures in theinterest of good operation, and also to aid the balance of the axialthrust on the rotating element, the inner casing 2 is provided with achamber 21 at its discharge end outwardly of the piston 25). The chamber21 has communication with the suction i through a plurality of internalconduits or pipes 23 which, as shown in Figures 1A and 13, extendlongitudinally of the pump structure and have no communication with thefluid flow through the normal flow passages 4 of the pump excepting onlythe suction I, but it is understood that while this type ofcommunication is shown that other means such as external conduits may beutilized for this purpose.

In some instances of multi-stage centrifugal pump construction, it maybe desirable either to add outlets to remove fluid at a pressure low--or than final discharge pressure of the pump, or to add inlets tointroduce fluid into the pump from some source in the system in whichthe pump is employed where the pressure of the introduced fluid is inexcess of the suction pressure. In either of such events, additionalpiston-like enlargements are formed on the inner casing to fit anotherouter casing bore to make a second slip joint and a second pressurechamher as more fully shown and described in my copending application,Serial No. 383,877, filed October 2, 1953.

Figure of the drawings shows a slight modification in the pump structurewherein the first stage of the multi-stage centrifugal pump is a doublesuction impeller 46, the suction eyes 41 at each. side of which receivethe incoming liquid from the branches d2 of the inlet passage 43 formedin the inner casing 44. The inlet passage 53 in the inner casing 44communicates with the inlet passage it in the outer casing 45 of thepump. An annular space 41 is provided between the outer casing 46 andthe inner casing 44 and has communication with the discharge 48 of theinner casing to receive fluid under discharge pressure of the pump and apiston-bore slip joint construction 49 is provided between the outercasing 46 and the inner casing 44; The slip joint construction isidentical in constructicn with the slip joint shown in Figure 1A of thedrawings, and it will permit relative longitudinal movement of the outerand inner. casing on expansion or contraction thereof and will alsoprovide a normal seal between the two casings. The inner casing 44 has achamber 50 therein at its discharge end which has communication throughsuitable pipes or conduits 5| with the suction 43 so that the surfacesurrounding the chamber 56 will be subjected to suction pressures of thepump. Like the pump shown in Figures 1A and 1B, the inner casing M has arelatively light connection flange 52 at its discharge end which isconnected with relatively light bolts 53 to its outer case 48. Such aconstruction is permitted due to the approximate counter-balancing ofthe forces whereby the net axial forces acting perpendicular to thelongi tudinal axis will be relatively small as above described.

Figure 8 and Figure 13 combined show the modified form of the inventionwhich permits complete external assembly of a complete operable pumpcarrying its own bearings by mere insertion of it in the outer casingand bolting up to be ready to function as a complete pump. Thisarrangement demonstrates clearly the versatility of this piston andbored cylinder construction for assembly and disassembly with a minimumamount of effort and allows for the complete re moval of one unit andreplacement thereof by a completely new unit without the necessity ofcompletely disassembling the entire pump structure.

The modified form changes in particular the suction side of the pump asis shown in Figure 8 of the drawings. This outer casing I is asubstantially cylindrically-shaped casing open at either end to receivetherein the inner casing 2' of the pump.

The outer casing I is now provided with a suction inlet 3 and dischargeoutlet shown in Figure 113 instead of a suction passage 1 as is shown inFigure 1A. It being understood that the suction inlet and dischargeoutlet may be varied in their respective positions to suit theparticular design as is immediately evident to one skilled in the art.

Inner casing 2' is constructed so that is is complete in itself as itcarries a suction passage 4' which communicates with the suction eye 5of the first stage impeller 6 which discharges into the various flowpassages 1' formed therein. Formed outwardly of the suction passage 4 isthe sealing structure 8 for the impeller shaft 9 and a bearing supportmember [0 to carry the bearings (not shown) which support the impellershaft 9' outwardly of the sealing'struc ture.

Thus, the inner casing 22 may be inserted longitudinally into the outercasing I with all of its assembled operative parts, so that the suctioninlet 3 will communicate with the suction passage 4 to form a completepump unit which is easily renewable by mere replacement of a newinternal unit-completely assembled.

The inner casing is further provided with annular pistons ii and I2 oneither side of the suction passage 4 which slidably engage cylindricalbored surfaces It formed in the o utercasing thus forming slip joints asis clearly shown in Figure 8 of the drawings. The pistons It and I2 andthe cylindrical surfaces 83 forming the slip joints are substantiallyidentical in construction with pistons [9 shown in Figure 1A of thedrawings, above described. To efiect better sealing against fluidleakage, however, 0 rings it have beenadded. It being understood thatac'zaooc other types of packing structures may be utilized as, forexample, that shown in Figure. 6 of the drawings.

By providing the piston-cylinder. slip joint between the outer barrelwithout longitudinal joints and the inner axially split casing of thepump, it is not necessary to provide. a complicated seal construction toprevent damage to the pump under fluid temperature changes in service,and the discharge end flange of the outer casing in the present pumpdoes not need to be made sufficiently heavy to carry the force resultingfrom the discharge pressure of the pump against the full area of thedischarge end closure member as above described.

It'will be understood that the invention is not to be limited to thespecific construction or arrangement of parts shown, but that these maybe widely modified within the invention defined by the claims.

What is claimed is:

1. In a multi-stage centrifugal pump or the he, a hollow cylindricalouter casing, an inner casing including a plurality of pumping stageshaving flow passages and impellers, said casing provided withcommunicating inlet and communicating discharge outlets, said outercasing bored internally to provide finished bores on the inner surfacethereof disposed on either side of said discharge outlets, said innercasing having diametral enlargements thereon corresponding to said.finished bores and mounted for sliding contact with said bores to format least one slip joint for expansion and. contraction of said innercasing with respect to said outer casing, at least one of said diametralenlargements formed on the end of said inner casing outward- 1y of saiddischarge outlets and provided with means thereon for connecting saidcasing, at one end, a chamber formedbetween said casings when saidcasings are disposed to form said slip joint, said chamber locatedbetween said discharge outlets and at least one of said slip joints andopen to receive fluid at discharge pressure from the discharge-outlet ofsaid. inner casing whereby said slip joint will be responsive topressure and temperature changes in said fluid being pumped, said innercasing having a second chamber therein at its discharge end formedoutwardly of said diametral enlargement having the connecting meansthereon, and means formed in said inner casing to establishcommunication between said second chamber and the inlet openings forsaid casings.

2. In a multi-stage centrifugal pump or the like as is claimed in claim1 wherein said means providing communication between said second chamberand said inlet openings for said casings includes, a conduit formedintegrally with said inner casing having an opening at one end into saidinlets and at the other end into said second chamber.

3. In a multi-stage centrifugal pump, a hollow cylindrical outer casing,an inner casing including a plurality of pumping stages having flowpassages and impellers, said casings provided with communicating inletsand communicating discharge outlets, said outer casing havingcircumferential sealing surfaces on the inner surface thereof disposedon opposite sides of the discharge outlet therein, said inner casinghaving continuous circumferential enlargements thereon corresponding tosaid sealing surfaces to form at least one slip joint and at least oneseal therewith, said outer casing, inner casing. and circumferentialenlargements forming a pressure chamber communicating with saiddischarge outlets, said slip joint and said seal having substantiallyequal diameters to present a relatively small net cross-sectional areasubject to the full discharge pressure acting between said casing, andmeans for connecting said inner casing to said outer casing.

4. In a multi-stage centrifugal pump, a hollow cylindrical outer casing,an inner casing including a plurality of pumping stages having flowpassages impellers, said casings provided with communicating inlets andcommunicating discharge outlets, said outer casing havingcircumferential sealing surfaces on the inner surface thereof disposedon opposite sides of the discharge outlet therein, said inner. casinghaving continuous circumferential enlargements thereon corresponding tosaid sealing surfaces to form at least one slip joint and at least oneseal therewith, said outer casing, inner casing and circum' ferentialenlargements forming a pressure chamber communicating with saiddischarge outlets, said slip joint and said seal having substantiallyequal diameters to present a relatively small net cross-sectional areasubject to the full discharge pressure acting between said casing, andmeans continuous with said inner casing for connecting said inner casingto said outer casing.

5. In a multi-stage centrifugal pump as claimed in claim 4 wherein meansto reduce leakage is provided on said slip joint between saidcommunicating inlets and said pressure chamber.

6. In a multi-stage centrifugal pump, a hollow cylindrical outer casinghaving an inlet and a discharge outlet, said outer casing having atleast onecircumferential sealing surface on the inner surface thereofdisposed between said inlet and said discharge outlet, an inner casingincluding a plurality of pumping stages having flow passages andimpellers and a suction inlet and discharge outlet for said inner casingcommunicating with said inlet and said discharge outlet of said outercasing, said inner casing having a continuous circumferentialenlargement thereon for sliding contact with said circumferentialsealing surface to form a slip joint therewith, a second circumferentialenlargement on said inner casing for contact with the inner surface ofsaid outer casing on the side of the discharge outlet thereof oppositefrom said slip joint to form a seal therewith, said outer casing, innercasing and circumferential enlargements forming a pressure chambercommunicating with said discharge outlets, said slip joint and saidformed seal having substantially equal diameters so that a relativelysmall. net cross-sectional area will be subject to the full dischargepressure acting between said casings, and means connecting said innercasing to said outer casing.

'7. In a multi-stage centrifugal pump, a hollow cylindrical outer casinghaving an inlet and a discharge outlet, 5 :id outer casing having atleast one circumferential sealing surface on the inner surface thereofdisposed between said inlet and said discharge outlet, an inner casingincluding a plurality of pumping stages having flow passages andimpellers and a suction inlet and discharge outlet for said inner casingcommunicat ing with said inlet and said discharge. outlet of said outercasing, said inner casing having a continuous circumferentialenlargement thereon for sliding contact with said circumferentialsealing surface to form a slip joint therewith, a second circumferentialenlargement on said inner casing for contact with the inner surface ofsaid outer casing on the side of the discharge outlet thereof oppositefrom said slip joint to form a seal therewith, said outer casing, innercasing and circumferential enlargements forming a pressure chambercommunicating with said discharge outlets, said slip joint and saidformed seal having substantially equal diameters so that a relativelysmall net cross-sectional area will be subject to the full dischargepressure acting between 10 said casings, said second circumferentialenlargement on said inner casing having means continuous therewith forconnecting said inner casing to said outer casing.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Name Date Aisenstein Oct. 15, 1935 Hollander Oct. 20, 1936Bigelow June 6, 1939 Nelson Apr. 17, 1945 Wislicenus Nov, 4, 1947FOREIGN PATENTS Country Date Great Britain Nov. 16, 1922 Great BritainJan. 17, 1939

